Enhanced two-photon amplification in superconductor-semiconductor plasmonic waveguides

We theoretically demonstrate significant enhancement of two-photon amplification by using a superconductor for both a Cooper-pair source and surface plasmon-polariton mode guiding. Cooper-pair-based gain active region restriction to the superconductor-semiconductor interface limits its potentially highly efficient two-photon gain process. Using the superconductor layer for a plasmonic waveguide structure allows strong photon confinement while reducing design and fabrication constraints. This results in three orders of magnitude enhancement of the superconducting two-photon gain (TPG) compared to superconductor-based dielectric waveguides. Moreover, a superconducting TPG produced by a plasmonic waveguide increases with carrier concentration, meeting practical device requirements. Our results pave the way for efficient two-photon amplification realization in nanoscale devices.